Method and system for dynamically positioning a vehicle relative to another vehicle in motion

ABSTRACT

A computer-implemented method is provided for automatically guiding a first vehicle to maintain a position relative to a second vehicle traveling in a given area. The method includes the steps of: (a) receiving location data on the first and second vehicles; (b) determining a legal travel path in the given area from the first vehicle toward an expected position of the second vehicle; (c) automatically controlling the first vehicle to travel along the legal travel path; and (d) repeating steps (a) through (c) to automatically move the first vehicle to a relative position from the second vehicle and then to automatically maintain the relative position as the first and second vehicles travel through the given area.

CROSS RELATED TO RELATED APPLICATION

This application is a divisional of and claims priority to U.S. patentapplication Ser. No. 13/281,012 filed on Oct. 25, 2011 entitled METHODAND SYSTEM FOR DYNAMICALLY POSITIONING A VEHICLE RELATIVE TO ANOTHERVEHICLE IN MOTION, which is hereby incorporated by reference.

BACKGROUND

The present application relates generally to automatically drivenvehicles and, more particularly, to a method and system forautomatically driving and dynamically positioning a vehicle relative toanother in motion.

BRIEF SUMMARY OF THE DISCLOSURE

In accordance with one or more embodiments, a computer-implementedmethod is provided for automatically guiding a first vehicle to maintaina position relative to a second vehicle traveling in a given area. Themethod includes the steps of: (a) receiving location data on the firstand second vehicles; (b) determining a legal travel path in the givenarea from the first vehicle toward an expected position of the secondvehicle; (c) automatically controlling the first vehicle to travel alongthe legal travel path; and (d) repeating steps (a) through (c) toautomatically move the first vehicle to a relative position from thesecond vehicle and then to automatically maintain the relative positionas the first and second vehicles travel through the given area.

In accordance with one or more further embodiments, a first vehicle isprovided that is configured to automatically maintain a positionrelative to a second vehicle traveling in a given area. The firstvehicle includes a vehicle drive system, an obstacle detection systemfor detecting obstacles in a vehicle travel path, a vehicle stateproperty estimation system for estimating state properties of thevehicle, and a microprocessor-based vehicle controller receiving datafrom the obstacle detection system and the vehicle state propertyestimation system. The vehicle controller is configured to: (i) receivelocation data on the first vehicle from the vehicle state propertyestimation system, and to receive location data on the second vehicle;(ii) determine a legal travel path in the given area from the firstvehicle toward an expected position of the second vehicle; (iii)automatically control the vehicle drive system to drive the firstvehicle along the legal travel path; and (iv) repeat (i) through (iii)to automatically move the first vehicle to a relative position from thesecond vehicle and then to automatically maintain the relative positionas the first and second vehicles travel through the given area.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration showing an exemplary tractor maintaining arelative position from a harvester in accordance with one or moreembodiments.

FIG. 2 is a simplified block diagram illustrating components of a firstvehicle in accordance with one or more embodiments.

FIG. 3 is a simplified illustration showing the trailer angle betweenthe tractor and a conveyance.

FIG. 4 is a simplified diagram illustrating an exemplary field in whichan automated tractor can operate.

FIG. 5 is a simplified state diagram illustrating various states of theautomated vehicle in accordance with one or more embodiments.

FIG. 6 is a simplified diagram illustrating a harvester.

FIG. 7 is a simplified diagram illustrating varying load positions in aconveyance.

FIG. 8 is a simplified diagram illustrating calculation of the tractorpath in accordance with one or more embodiments.

Like or identical reference numbers are used to identify common orsimilar elements.

DETAILED DESCRIPTION

Various embodiments disclosed herein are directed to methods and systemsfor automatically driving and dynamically positioning a vehicle(referred to herein as a “first” vehicle) relative to another vehicle(referred to herein as a “second” vehicle). In some embodiments, thefirst vehicle is towing a conveyance, and it is controlled such that theconveyance is positioned accurately relative to the second vehicle,while the second vehicle is in motion. In some embodiments, the firstvehicle is controlled to move between a designated parking area and aposition relative to the second vehicle.

Such methods and systems can have a variety of applications including,e.g., agricultural applications. By way of example, as shown in FIG. 1,the first vehicle is an automatically driven tractor 10, the towedconveyance is a grain cart 12, and the second vehicle is a harvester 14.The parking area contains a semi truck into which the grain cart 12 isoffloaded after having been filled. In this example, the harvester 14offloads harvested corn, soy, or other product into the grain cart 12 asthe grain cart 12 is towed alongside the harvester 14 by the tractor 10.When the grain cart 12 is filled, the tractor 10 tows it to the parkingarea to be offloaded into the semi truck. When the grain cart 12 isempty, the tractor 10 tows it back out to the harvester 14, which hasremained in motion, to begin taking offloaded product again.

For simplicity, various exemplary embodiments disclosed herein refer tothe grain cart example. However, it should be understood that there aremany other possible applications for the methods and systems describedherein, including agricultural and non-agricultural applications. Otherpossible applications can include, but are not limited to, mining, oiland gas exploration, defense, first response, and materials handling.

The second vehicle 14, which the first vehicle 10 is controlled to bepositioned relative thereto, can be operated in various ways, includingby a human driver inside the vehicle. Alternately, the second vehicle 14can be tele-operated (i.e., remotely operated) by a human outside thevehicle or it can be driven entirely automatically.

Various embodiments disclosed herein discuss the positioning of thetowed conveyance 12 relative to the second vehicle 14. However,techniques disclosed herein are also applicable to the case where thesecond vehicle 14 is also towing a conveyance, and the dynamicpositioning of the first conveyance is relative to the secondconveyance. In some embodiments, the second vehicle 14 can tow aconveyance, and the dynamic positioning of the first vehicle 10 isrelative to the conveyance of the second. In further embodiments,neither vehicle tows a conveyance, and the first vehicle 10 iscontrolled such that it is dynamically positioned relative to the secondvehicle 14.

FIG. 2 is a simplified block diagram illustrating components of theautomated first vehicle 10 in accordance with one or more embodiments.The first vehicle 10 includes a vehicle drive system 16 or chassis formoving the vehicle. The first vehicle 10 also includes an obstacledetection system 18 including one or more range sensors for detectingobstacles 36 (shown in FIG. 4) in the vehicle travel path. The firstvehicle 10 also includes a vehicle state property estimation system 20comprising one or more sensors for estimating state properties of thevehicle. It further includes a microprocessor-based vehicle controller22, which receives inputs from the obstacle detection system 18 and thevehicle state property estimation system. The vehicle controller 22 alsoreceives data on estimated state properties from the second vehicle 14.The vehicle controller 22 controls operation of the drive system 16 andis programmed to maneuver the vehicle in a desired manner, includingdynamically positioning the first vehicle 10 relative to the secondvehicle 14.

In various exemplary embodiments described herein, the vehiclecontroller 22 is physically located within the body of the first vehicle10. It should be understood, however, that in other embodiments, thevehicle controller 22, or portions of the controller, could be locatedoutside of the first vehicle 10. Such separation of physical location ofthe electronics and software for controlling the first vehicle 10 iscontemplated herein. Moreover, while in the exemplary embodimentsdiscussed herein indicate information is sent to or from the firstvehicle 10, that is intended to mean information sent to or from thevehicle controller 22, wherever it may be physically located.

Determining Vehicle Positions

The vehicle state property estimation system 20 in the first vehicle 10estimates several state properties of the vehicle from one or moresensors. Similarly, the second vehicle 14 includes a vehicle stateproperty estimation system to estimate several state properties of thatvehicle. State variables estimated for both vehicles include absoluteposition in some Earth-relative navigation system (e.g., latitude andlongitude), speed, heading, and yaw rate (i.e., rate of change ofheading). For the first vehicle 10, the angle between the vehicle 10 andany towed conveyance 12 (e.g., between the tractor 10 and the grain cart12 as illustrated in FIG. 3) is also estimated.

By way of example, a set of sensors for forward motion comprise a GlobalPositioning System (GPS) device with Real Time Kinematic (RTK)correction, which provide position and, when a vehicle is in motion,heading. The set of sensors can further include an inertial measurementunit (IMU), which provides measurements of linear acceleration androtational velocity. The set of sensors can also include sensors forodometry measurements of the tractor's wheels and steering angle. Othercombinations of sensors are also possible for forward motion.

To enable reverse motion of a vehicle 10 with a towed conveyance 12 on ahinged hitch, an additional sensor is used, which directly or indirectlymeasures the angle between the vehicle 10 and the conveyance 12. Thisadditional sensor is used because reverse motion is generally unstable,and dynamic control techniques are performed using the sensor input.

By way of example, the desired state values can be estimated from thesensor data using an Unscented Kalman Filter (UKF), whose inputs are thesensor measurements and whose outputs are the state variables. Otherstate estimation methods could also be employed.

Both vehicles need not use the same set of sensors. For instance, theharvester 14 could use the global, earth-relative sensors describedabove, while the tractor 10 could use sensors that directly ascertainits position relative to the harvester 14 in some local reference frame.

Relative positioning is the responsibility of the automatic tractor 10.Thus, the state estimates of the harvester 14 are continuously sentelectronically to the tractor 10 to facilitate positioning.

Legal Travel Areas

FIG. 4 is a simplified illustration of an exemplary field 24 on whichthe tractor 10 and harvester 14 can operate. The field 24 is defined bya field boundary 26. The field 24 includes legal travel areas within thefield boundary 26. The tractor 10 is allowed to travel only in the legaltravel areas.

Legal travel areas can include a designated parking area 28. The systemoperator may designate zero or more geographic regions of arbitraryshape to be parking areas.

Legal travel areas can also include designated travel corridors 30. Thesystem operator can designate zero or more geographic regions ofarbitrary shape to be travel corridors.

Legal travel areas can also include previously traveled areas. If thesecond vehicle 14 travels over an area, that area is by default deemedto be a legal travel area. For instance, a harvester 14 harvests thecrop and leaves a cleared area behind it. The harvester 14 regularlytransmits newly-cleared path information to the tractor controller 22 sothat the tractor 10 has an accurate representation of the harvestedareas.

The field boundary 26 can be designated by the system operator as anarbitrary boundary around the operating area. No area outside of thatboundary can be a legal travel area.

The system operator can also designate an arbitrary boundary 32 aroundzero or more obstacles. No area inside any obstacle boundary 32 can be alegal travel area.

The obstacle detection system 18 in the first vehicle allows it todetect unanticipated obstacles 36 in the field 24. While an obstacle 36is detected, it designates an obstacle boundary 32 around the obstacle.This area within the obstacle boundary 32 is not a legal travel area.

Long-distance Path Finding

When the second vehicle 14 is a sufficiently long distance away from thefirst vehicle (e.g., the tractor 10 is in a parking area 28 and theharvester 14 is operating in the field 24), a long-distance path findingprocedure is used to determine a legal path for the first vehicle 10 tofollow to be at a desired position relative to the second vehicle 14. Avariety of algorithms and processes can be used for such long-distancepath finding, including a standard A* or hybrid A* algorithm. The A*algorithms work from a discrete set of moves—that is, a discrete set ofvehicle headings is considered at each step in the process.

The area available for the path planning algorithms to use is determinedfrom both the pre-surveyed paths in the field 24 (e.g., designatedparking areas 28, travel corridors 30, field boundaries 26, and obstacleboundaries 32) and area 34 that has been previously travelled by theharvester 14.

The algorithm for checking whether a path lies entirely inside legaltravel areas can use a simplified polygon representation of the vehicleand the legal travel areas, and performs intersection-checking of thevehicle polygon with the various areas.

In accordance with one or more embodiments, to reduce the frequency withwhich the tractor 10 has to “stop to think,” it runs a path planningalgorithm tuned to run to conclusion quickly, but to give up relativelyeasily on any path. In order to find a path even in complex terrain, thetractor 10 simultaneously runs a copy of the path planning algorithmtuned to be very aggressive in trying to find a path. This ensures thatif the quick path finder above fails, the tractor 10 can eventuallythink its way out of any solvable situation.

Operator Commands

The system operator can issue various high-level commands (shown in FIG.5) to the automatic tractor 10, including STOP 50, EMERGENCY STOP 52,PARK 54, FOLLOW 56, and OFFLOAD 58A, 58B. As shown in FIG. 5, any statecan transition to STOP 50 or EMERGENCY STOP 52.

Upon receiving a STOP command 50, the tractor 10 will slow to a haltalong its currently planned path. The manner of stopping is intended tobe as quick as possible while remaining subjectively comfortable for anyhuman occupant of the tractor 10.

When executing an EMERGENCY STOP operation 52, the tractor 10 willattempt to halt as quickly as possible, e.g., by fully engaging thebrakes and fully disengaging the clutch. The manner of stopping isintended to be immediate, without regard to the subjective comfort ofany human occupant of the tractor 10.

When executing a PARK operation 54, the tractor 10 will performlong-distance path finding to find a legal path to the designatedparking area 28. If a path is found, the tractor 10 will travel usingthe long-distance path following process. If no path is found, thetractor 10 will perform a STOP operation 50, returning to active motionwhen a legal PARK path is discovered.

Upon receiving FOLLOW command 56, the tractor 10 will perform a FOLLOWoperation to begin following the harvester 14 at a standoff distance. Ifthe harvester 14 is not nearby when the operation starts, the tractor 10will first transit from its current location to the harvester 14 vialegal long-distance travel paths, using the long-distance path followingprocess. If no legal path can be determined, the tractor 10 will begin aSTOP operation 50, returning to active motion when a legal FOLLOW pathis discovered.

As the harvester 14 moves, the tractor 10 creates new plans to thecurrent harvester position. The plan is made from a point in thetractor's future path. If an updated plan is found successfully, theremainder of the current plan is replaced with the new plan. This updateand re-plan procedure continues indefinitely while the tractor 10 is inFOLLOW mode 56.

Upon receiving an OFFLOAD command, the tractor 10 will perform anOFFLOAD operation 58A, 58B to take up a precisely-maintained positionrelative to the harvester 14 to support offload.

The harvester 14 can include a lever arm 70 (shown in FIG. 6) foroffloading material to the grain cart 12. The system operator identifiesa position relative to the harvester 14, called the “lever arm position”or “spout position” 72 (shown in FIG. 6), and a position relative to thegrain cart 12, called the “load position” 74 (shown in FIG. 7). Duringthe OFFLOAD operation, the system endeavors to keep the two positionsco-located.

The OFFLOAD process is comprised of two major steps. In the first step,ROUGH POSITIONING 58A, the automatic tractor 10 tows the trailer 12 intoa “roughly correct” position using the long-distance path finding andlong-distance path following processes to get near the harvester 14. Ifthe tractor 10 cannot determine a legal path to an offload position, orif the tractor 10 is already in offload position, but the current legalpath “dead ends,” it will perform a FOLLOW operation 56 until such timeas a legal offload path can be found.

The second step, FINE POSITIONING 58B, begins once the trailer 12 is inapproximately the correct position, to bring it to the desired position,and to maintain that position, with the required accuracy. In this mode,the tractor 10 uses the state information received from the harvester 14to estimate the arc that the lever arm position will trace out, assumingthat the current harvester yaw rate remains constant. A standard controlalgorithm known as “pure pursuit” can be used to determine the path thatthe grain cart should traverse in order to keep the load position 74co-located with the spout position 72.

Given the grain cart's required path and current position, the anglealpha between the automatic tractor 10 and the grain cart 12 can bedetermined given simple models of each element. The automatic vehicle 10is then steered to create the desired “alpha” 76 as shown in FIG. 8using a standard PID controller integrated into the vehicle controller22.

Offload Position Targeting

The harvester vehicle 14 may support more than one lever arm position.For example, a harvester 14 may support offloading to the right or tothe left sides.

In some embodiments, the load position 74 can be deliberately varied (asshown in FIG. 7) during operation, e.g., in order to maintain even fillof a grain cart 12. The system operator may manually adjust the loadposition 74 during operations. The load position 74 may also optionallybe set to automatically cycle from the front of the grain cart to theback. Furthermore, the use of sensors such as load sensors orcontent-height sensors affixed to the grain cart at various points canbe used to automatically guide the loading position 74 along the axis ofthe grain cart 12 to provide more even loading.

The processes of the vehicle controller 22 described above may beimplemented in software, hardware, firmware, or any combination thereof.The processes are preferably implemented in one or more computerprograms executing on the vehicle controller 22. Each computer programcan be a set of instructions (program code) in a code module resident inthe random access memory of the controller 22. Until required by thecontroller 22, the set of instructions may be stored in another computermemory (e.g., in a hard disk drive, or in a removable memory such as anoptical disk, external hard drive, memory card, or flash drive) orstored on another computer system and downloaded via the Internet orother network.

Having thus described several illustrative embodiments, it is to beappreciated that various alterations, modifications, and improvementswill readily occur to those skilled in the art. Such alterations,modifications, and improvements are intended to form a part of thisdisclosure, and are intended to be within the spirit and scope of thisdisclosure. While some examples presented herein involve specificcombinations of functions or structural elements, it should beunderstood that those functions and elements may be combined in otherways according to the present disclosure to accomplish the same ordifferent objectives. In particular, acts, elements, and featuresdiscussed in connection with one embodiment are not intended to beexcluded from similar or other roles in other embodiments. Additionally,elements and components described herein may be further divided intoadditional components or joined together to form fewer components forperforming the same functions.

Accordingly, the foregoing description and attached drawings are by wayof example only, and are not intended to be limiting.

What is claimed is:
 1. A computer-implemented method for automaticallyguiding a first vehicle to maintain a position relative to a secondvehicle traveling in a given area, said first and second vehicles beingindependently driven and being unattached to each other, the methodcomprising the steps of: (a) receiving location data on the first andsecond vehicles; (b) determining a legal travel path for the firstvehicle in the given area from the first vehicle toward an expectedposition of the second vehicle; (c) automatically controlling the firstvehicle to travel along the legal travel path; and (d) repeating steps(a) through (c) to automatically move the first vehicle progressivelycloser to the second vehicle until the first vehicle is at a givenrelative position from the second vehicle and then to automaticallymaintain the given relative position as the first and second vehiclestravel through the given area.
 2. The method of claim 1, wherein thelocation data on the first and second vehicles comprises estimated stateproperties of each vehicle based on data received from one or moresensors.
 3. The method of claim 2, wherein the state properties comprisean absolute position in a shared reference frame, speed, heading, andyaw rate.
 4. The method of claim 2, wherein the first vehicle tows aconveyance, and wherein the state properties include an estimation of anangle between the first vehicle and the towed conveyance.
 5. The methodof claim 2, wherein the one or more sensors comprise forward motionsensors including a Global Positioning System (GPS) sensor with RealTime Kinematic (RTK) correction, an inertial measurement unit (IMU), oran odometer.
 6. The method of claim 1, wherein the first vehicle tows aconveyance, and wherein moving the first vehicle to a relative positionfrom the second vehicle comprises co-locating a given offload positionin the conveyance with a mechanism extending from the second vehicle. 7.The method of claim 6, wherein the first vehicle is a tractor and theconveyance is a cart, and wherein the second vehicle comprises aharvester and the mechanism comprises a lever arm for offloadingharvested material from the harvester to the cart.
 8. The method ofclaim 6, wherein the given offload position in the conveyance is variedto maintain a generally even fill of the conveyance.
 9. The method ofclaim 8, wherein the given position in the conveyance is varied manuallyor automatically in accordance with a predetermined pattern or based oncontent-height sensor readings.
 10. The method of claim 1, wherein thesecond vehicle tows a conveyance, and wherein moving the first vehicleto a relative position from the second vehicle comprises co-locating agiven position in the conveyance with a mechanism extending from thefirst vehicle.
 11. The method of claim 1, wherein the second vehicle isoperated by a human driver inside the vehicle, tele-operated by humanoutside the vehicle, or automatically driven.
 12. The method of claim 1,further comprising automatically driving the first vehicle to a parkingarea in response to receiving a park command.
 13. The method of claim 1,further comprising automatically stopping the first vehicle in responseto a stop command.
 14. The method of claim 1, further comprisingautomatically driving the first vehicle to follow the second vehicle ata standoff distance in response to follow command.
 15. The method ofclaim 1, wherein the method steps are implemented in a computerizedvehicle controller, and wherein the controller is installed in the firstvehicle or is installed in a location remote from the first vehicle andtransmits control signals to a drive system in the vehicle.
 16. Themethod of claim 1, wherein any portion of the given area previouslytraveled by the second vehicle is a legal travel area.
 17. The method ofclaim 1, wherein the given area is defined by an outer boundary, and alegal travel path must be within the outer boundary.
 18. The method ofclaim 1, wherein a legal travel path cannot extend through any portionof a predetermined obstacle boundary.